Sealing Washers vs. Non-Sealing Washers: What’s the Difference?

Washers may seem like simple hardware, but they serve a critical function in keeping fasteners secure. While all washers help distribute force and protect surfaces, some go a step further by providing a reliable seal against dust, moisture, and other contaminants.

So, what’s the difference? Sealing washers protect against environmental intrusion, while non-sealing washers serve only mechanical purposes. Choosing the right type can impact everything from long-term equipment performance to safety and maintenance costs. Here, we’ll break down how sealing and non-sealing washers differ—and when to use each.

What Are Non-Sealing Washers?

Non-sealing washers are standard washers designed for mechanical support only. They do not block water, air, or contaminants.

Primary functions include:

• Distributing load to prevent material damage
• Protecting surfaces from scratches or distortion
• Helping mainting bolt or screw tension

Common types of non-sealing washers include:

• Flat washers: Basic washers that spread the load
• Lock washers: Prevent loosening from vibration
• Spring washers: Apply a consistent force to help maintain tension

These washers are ideal for dry, indoor, or low-risk environments where sealing is not needed.

What Are Sealing Washers?

Sealing washers combine mechanical function with environmental protection. Unlike standard washers, they are designed to prevent leaks and block out contaminants like dust, moisture, and debris.

These washers typically consist of a metal backing bonded to an elastomer such as silicone, neoprene, or EPDM. When compressed, the elastomer forms a tight, lasting seal under the fastener head and around the shank.

Sealing washers are used in:

• Electrical enclosures and control panels
• Outdoor machinery and marine equipment
• Automotive, aerospace, and industrial systems

APM Hexseal’s Seeloc^® Washers feature a silicone contact surface with a continuous ridge that creates a 360° seal. This design helps protect sensitive components from both leaks and environmental intrusion, even under pressure, vibration, or extreme temperatures.

Key Differences

How To Choose the Right Washer For Your Application

Non-sealing washers are best for applications where only mechanical support is needed. Use them to distribute load, protect surfaces, or maintain bolt tension in dry, indoor environments. They offer a simple, cost-effective choice when sealing isn’t a concern.

Sealing washers should be used when the application is exposed to moisture, dust, oil, or other contaminants. They’re ideal for protecting sensitive components in outdoor, marine, automotive, or industrial equipment. Sealing washers also perform well in high-vibration or high-pressure environments, where maintaining a tight seal is critical. They are also UL recognized making them a great fit for NEMA rated enclosures and their reusability makes them a smart economic choice for applications that require frequent access or maintenance.

If environmental protection is important but you want to avoid redesigning your fastener system, sealing washers provide a practical solution. Their dual function makes them an efficient choice in demanding settings.

APM Hexseal’s Sealing Washer Solutions

Both sealing and non-sealing washers play important roles in fastening systems. Non-sealing washers are suitable for standard mechanical support, while sealing washers offer added protection in harsh or unpredictable environments. Understanding when and where to use each type can help improve performance and extend equipment life.

APM Hexseal specializes in sealing solutions that meet the needs of the most demanding applications. Our Seeloc^® Washers are designed to maintain airtight, watertight seals even under pressure, vibration, and extreme environmental conditions. Contact us to learn more about our Seeloc^® Washers, or request a quote for your next project.